Thinking of buying 85ft. Hatt extended MY

[scottinsydney]

My 61MY has a 9' extension. The hull is surprisingly shallow under the extension and only 8" of hull is under water at the transom. The rudders appear to be greatly enlarged from the originals I have seen in others' photos. They seem much taller.

I've seen my boat in 50 knot bow on winds and medium following seas, with and without stabilisers. It seemed fine to me. In calm conditions it tracks pretty straight with no meandering.

The boat lives on a swing mooring and once every two weeks comes into the marina end which necessitates a very tight 180" uturn. I do this uturn on the spot without turning the rudders. If I ever use rudder to help, the turn is faster. I just feel the pivot spot is more towards the centre of the boat. I can corkscrew away from a wharf without rudders or bow thruster,... just need a little space.

Hope this aids this interesting discussion.

[WA2DDL]

My 61MY has a 9' extension. The hull is surprisingly shallow under the extension and only 8" of hull is under water at the transom. The rudders appear to be greatly enlarged from the originals I have seen in others' photos. They seem much taller.

I've seen my boat in 50 knot bow on winds and medium following seas, with and without stabilisers. It seemed fine to me. In calm conditions it tracks pretty straight with no meandering.

The boat lives on a swing mooring and once every two weeks comes into the marina end which necessitates a very tight 180" uturn. I do this uturn on the spot without turning the rudders. If I ever use rudder to help, the turn is faster. I just feel the pivot spot is more towards the centre of the boat. I can corkscrew away from a wharf without rudders or bow thruster,... just need a little space.

Hope this aids this interesting discussion.

Thanks for the info. I am not sure exactly what to think about this extension situation vs. handling. I really don't think the owner is trying to lie to me and I know handling is subjective in itself, but you brought up an interesting item...larger rudders. Perhaps this boat has larger ones, as well. I put out a request for info from the owner, but he is on a seagoing tug for a couple weeks and might not get back right away. Even if he did, he might not know since the extension was accomplished two owners previous to him.

But, knowing the forces would need to be greater for a turn, wouldn't the yard - which lengthens hulls on a regular basis - know that larger rudders need to be fitted? I would think that makes basic sense.

Thanks again for chiming in, would like to hear anything additional you might have.

BTW, does anyone know if a hull extension would automatically equal a rudder change? If the owner of this Hatt, the one I am thinking of buying, is correct about the handling being "better" than before the extension, it would almost HAVE to be because of a rudder swap.

Anyone also have any blistering stories for earlier hulls (70's and 80's)? Mine is a '77.

[Walter P]

Larger rudders seem very logical.

Walt

[WA2DDL]

Larger rudders seem very logical.

Walt

I would think so, Walt. With all of our discussions on this thread, I can only guess that larger rudders are an automatically included part of any hull extension project.

In aerodynamic weight and balance, if the arm (distance) becomes shorter, the moment (force) must increase. Hydrodynamics cant be much different.

Going in depth here, the increase weight in the aft area, because of the extension, will bring the CG (Center of Gravity) aft somewhat. This change in CG location will shorten the arm between the CG and rudder area. When you shorten the arm you need to increase the moment, and one way to do this is to increase the size of the rudder, thus increasing the force and allowing the boat to pretty much respond as before the extension.

...Anyway, it works that way in airplanes.

[WA2DDL]

Walt,

Did you have any blistering problems with either your hull or deck?

[Cricket]

My guess is that there are no "standard" additions for an extension, or any other custom work to a boat.
Personally I think most of the older Hatts were under ruddered from the factory. Not that there's much relevance between our 50c and an 85my; people that are on our boat for the first time are surprised how quickly it turns at slow/trolling speed with both engines in forward. We have even cut the rudders down twice since we installed them during the CAT repower. Anyone that doesn't have power steering should really think about adding it, it's a game changer, ours is under 2.5 turns lock to lock.

[oscarvan]

I would think so, Walt. With all of our discussions on this thread, I can only guess that larger rudders are an automatically included part of any hull extension project.

In aerodynamic weight and balance, if the arm (distance) becomes shorter, the moment (force) must increase. Hydrodynamics cant be much different.

Going in depth here, the increase weight in the aft area, because of the extension, will bring the CG (Center of Gravity) aft somewhat. This change in CG location will shorten the arm between the CG and rudder area. When you shorten the arm you need to increase the moment, and one way to do this is to increase the size of the rudder, thus increasing the force and allowing the boat to pretty much respond as before the extension.

...Anyway, it works that way in airplanes.

Hmmm I'm not an engineer either but a few observations on your statement.

The rudders provide an effort (force) upon the vertical axis. CG acts on the lateral axis. The boat will pivot around something called the "center of lateral resistance". THIS point has also moved with the extension, as the hull shape has changed significantly. And yes it has moved aft, closer to the rudders. You are correct that the arm of the rudders has changed (decreased in fact) and thus the rudders need to be increased in size to arrive at the same turning force. But it's IMO not the arm to the CG that matters. CG and CLR are not necessarily co-located.

Where weight WILL matter is the fact that the inertia (from stop to turning movement as well as from turning movement to stop) will also have increased and this too will require increased rudder force.

[miboatnutz]

I am an engineer. Lol!

The fact that you don't have any info on the rudders for this boat ought to tell you something right there. Not trying to be overly critical but we could "armchair" this thing until the cows come home. Your best bet if you're serious about purchasing the vessel would be to have a competent marine surveyor perform a very comprehensive survey based on a detailed scope of work.

Survey should include such items as size and condition of the rudders, steering system and drivetrain. In addition, I'd have him/her document the size, shape, thickness and condition of all the scantlings and connections for the extension as well as hull bottom and topside thickness and moisture content from stem to stern. This would be in addition to all the usual inspection items for the survey.

Of course, I'd also have a diesel mechanic survey the engines as well. This is all normal course of business in purchasing a used boat.

If those two exercises don't turn up any roadblocks, I'd then take the added step of hiring a naval architecture/marine engineering consultant to evaluate the extension. Again with a detailed scope of work, I'd have them perform the engineering calculations for performance and structural integrity that you should have gotten from the very beginning if you had commissioned this kind of retrofit from a reputable yard.

I would then use the results of the survey, diesel mechanic survey and naval architecture/marine engineering evaluation as negotiating tools for the final purchase of the boat assuming there are no "show stoppers along the way. If the naval architect says the boat should have had bigger rudders with the extension, then the price is adjusted down accordingly.

Also keep in mind that a marine surveyor is an inspector and not an engineer. His job is to report on the current condition of the vessel and not necessarily whether it was designed properly with or without the extension.

Finally I'd ask the current owner if he'd be willing to split the costs of the surveys and engineering evaluation if you're willing to share that info with him, irrespective of whether you buy the boat or not, as it would ultimately help him. If he refuses then take all those costs off your offering price.

IMHO that boat is not worth $365K in today's market.

[WA2DDL]

I am an engineer. Lol!The fact that you don't have any info on the rudders for this boat ought to tell you something right thereIMHO that boat is not worth $365K in today's market.

Well, the reason that I am on this thread is to read all posts and consider all sides of this equation. To be honest it sounds like if I did all of those things the cost of my boat would probably be double just in surveying charges, however let me address the rudder situation first.The owner may or may not have information on the Rudders and the hull itself. He owns a seagoing tugboat along with his son and is out on it right now for several weeks. I have put in a couple of texts to him and I have not heard anything back. Reason I'm saying this is because he may have all the information necessary, I just don't know about it because I haven't asked.That being said you brought up an interesting point that I think was posted once before... Maybe it was by you, probably someone else, but they said that they did not think the boat was worth that kind of money. So, what amount was in the back of your head when you wrote this? 300K? 250k? Let me know what you think about the price on this. Personally I think it would be impossible to find a vessel whose LOA is close to 90 feet in perfect shape in the $300,000 Market. There's got to be something wrong usually the interior is a little bit old. That's the case here but without a survey I don't know what the bottom line is going to be as far as the condition of the engines and generators, as well as smaller power units like Thruster and stabilizers.I appreciate your chiming in with this more than you know, but also would like to find out what number you had in mind if the 368k was too high.

[jim rosenthal]

Boats that have been modified are seldom worth more than a similar unmodified example of the same model and year. An exception might be, for example, an older boat that had had a complete repower with modern engines, or a complete interior refit. Maintenance items such as painting the boat, barrier coating the bottom, etc, wouldn't count; any boat will need them. I'm thinking more of major capital expenditures and changes from the original conformation and design.

In this instance, it seems to me that the worth of the boat would be established on 1) what someone is willing to pay for it, first and last 2) the worth of comparable original boats (the problem would be how much to add or subtract for the modifications) 3) the overall condition of this individual boat 4) an evaluation by an experienced captain of the handling characteristics of the boat, since the hull has been modified 5) the willingness of an insurance company to insure a modified vessel.

I have seen or seen mentioned several older Hatteras MYs which were lengthened- I even saw one being done years ago, here in Annapolis. So this is not all that unusual. But since it is a one-of-a-kind vessel, a lot of the usual rules don't apply, and notwithstanding all the conjecture about how she'll handle in the ocean and when you're docking her, what you will really need is a very experienced captain at the helm when you do the sea trial.

As to what she's worth, well, the fact that she's been for sale for a long time, if I understand correctly, might tell you something about that. As for the fact that she's owned by someone who makes his living as a captain- well, that may speak well of the vessel, or it may just mean that he's even crazier than the usual run of folks in this forum, which is really saying something, indeed.